Optimization of Clutch Characteristics to Improve the Launch Performance of a Sports-Utility Vehicle 2020-28-0481

Vehicles with manual transmission are still the most preferred choice in emerging markets like India due to their benefits in cost, simplicity and fuel economy. However, the ever-increasing vehicle population and traffic congestion demand a smooth clutch operation and a comfortable launch behaviour of any manual transmission vehicle. In the present work, the launch performance of a sports-utility vehicle (SUV) equipped with dual mass flywheel (DMF) and self-adjusting technology (SAT) clutch could be improved significantly by optimizing the clutch system.

The vehicle was observed to be having a mild judder during clutch release (with 0% accelerator pedal input) in a normal 1^st gear launch in flat road conditions. An extensive experimental measurement at the vehicle level could reveal the launch judder is mainly due to the 1st order excitation forces created by the geometrical inaccuracy of the internal parts of the clutch system. Moreover, the forces are amplified by the resonance of the complete driveline with the first eigen mode at 8 to 12 Hz. A detailed study in the 1-dimensional torsional simulation model revealed that the eigen mode frequency of the real-wheel drive architecture is mainly driven by several parameters (mass, inertia, torsional stiffness) of the driveline components. Hence, the 1st order excitation forces were needed to be controlled to improve the launch performance. Based on the detailed design of experiments (DOE), it was evident that the cushion disc stiffness and clutch disc parallelism are the significant contributors to the excitation forces. The launch performance of the vehicle could be significantly improved by reducing the cushion disc stiffness at lower axial load (300 N) and by controlling the clutch disc parallelism within a tight tolerance range. The effect of these modifications on different launch conditions is also explained in detail in the present work. The paper gives a holistic view of improving the launch performance of any vehicle without compromising any other parameter.